Optically sensitized silver halide emulsions

ABSTRACT

In a photographic silver halide emulsion spectrally sensitizing the emulsion with a sensitizer of the general formula   IN WHICH X is a sulfur, selenium or oxygen atom, or a group -CH CH-; n is 1-5; RI is an ethyleneoxy or a 1,2-propyleneoxy unit; RII is a saturated or unsaturated aliphatic group having up to five carbon atoms, suitably substituted; RIII is a monomethine group substituted with a five- or sixmembered heterocyclic ring containing nitrogen as ring member; or a trimethine, pentamethine or heptamethine chain carrying in the terminal position an oxazole, benzoxazole, naphthoxazole, thiazoline, thiazole, benzothiazole, naphthothiazole, selenazole, benzoselenazole, naphthoselenazole, thiadiazole, imidazole, benzimidazole or 2- or 4-quinoline ring, or a dimethine or tetramethine which carries in the terminal position a rhodanine, thiohydantoin, thiobarbituric acid or pyrazolone radical, or a rhodanine, thiohydantoin, thiobarbituric acid or pyrazolone radical.

United States Patent [72] Inventors JohannesGotze [54] OPTICALLY SENSITIZED SILVER HALIDE EMULSIONS 4 Claims, 6 Drawing Figs.

[52] US. Cl 96/138, 96/132, 96/133, 96/135, 96/137, 96/139, 96/140, 96/142 [51] Int.Cl G030 1/10, G03c 1/08 [50] Field of Search 96/ 102,

[56] References Cited UNITED STATES PATENTS 2,928,839 3/1960 Roth et al. 96/106 7/1965 Gotze 96/106 Primary Examiner-J. Travis Brown Attorney-Connolly & Hutz ABSTRACT: In a photographic silver halide emulsion spectrally sensitizing the emulsion with a sensitizer of the general formula X in which X is a sulfur, selenium'or oxygen atom, or a group C H CH- n is 1-5; 9

R is an ethyleneoxy or a 1,2-propyleneoxy unit;

R" is a saturated or unsaturated aliphatic group having up to five carbon atoms, suitably substituted;

R is a monomethine group substituted with a fiveor six-membered heterocyclic ring containing nitrogen as ring member; or a trimethine, pentamethine or heptamethine chain carrying in the terminal position an oxazole. benzoxazole, naphthoxazole, thiazoline, thiazole. benzothiazole, naphthothiazole, selenazole, benzoselenazole, naphthoselenazole, thiadiazole, imidazole, benzimidazole or 2- or 4-quinoline ring, or a dimethine or tetramethine which carries in the terminal position a rhodanine, thiohydantoin, thiobarbituric acid or pyrazolone radical, or a rhodanine, thiohydantoin, thiobarbituric acid or pyrazolone radical.

PATENTEnucI 26 I97! 3,615,644

'' sum 10F 2 INVENTORS Johannes Gb'tze, Oakar RiestcrQ PATENTEDIJET 25 mm 3,515, 44

' SHEET 2 0F 2 INVENTORS Johannes (32311270; Oskar- RtczsLur.

I If/um "1 10 OPTICALLY SENSITIZED SILVER HALIDE EMULSIONS The invention relates to nitrogen-containing heterocyclic compounds of the benzazole type, e.g., benzothiazole, benzoselenazole, benzoxazole or quinoline compounds, which are substituted by a hydroxyhcontaining aliphatic ether group, and to the use of such compounds as spectral sensitizers for photographic silver halide emulsions.

Benzazoles are known per se in many different forms. One of the most important uses for compounds which contain these heterocyclic groups is in the photographic field. The majority of the most important cyanine sensitizing dyes which are used in practice contain benzothiazole, benzoselenazole, benzoxazolc or quinoline groups.

It is among the objects of the invention to produce benzazole compounds. Another important object of the invention is to increase the sensitivity of photographic silver halide emulsions by sensitizing with new sensitizers.

it has now been found that benzothiazole, benzoselenazole, benzoxazole or quionoline compounds, in which the benzene ring contains a hydroxyl-containing aliphatic monoether or polyether substituent can be prepared in a simple manner. The compounds according to the invention correspond to the fol- H(R )DO in which X is a sulphur, selenium or oxygen atom, or the group CH=CH; n is 1-100, preferably 1-10, and in particlar 1-5;

R is an organic radical, e.g., an alkyl radical preferably with up to three carbon atoms, in particular methyl or an alkylthio radical, also preferably containing up to three carbon atoms, in particular methylthio,

R is an ethyleneoxy or 1,2-propyleneoxy group, which may be substituted e.g., with a phenoxy group;

R" is a saturated or unsaturated aliphatic group preferably containing up to five carbon atoms, in which the alkyl groups may be substituted, for example with sulfonic acid, sulfamyl, carboxyl, carbamyl or hydroxyl groups or with halogen atoms, such as chlorine;

R' is an organic radical, preferably a. a monomethine group which carries a heterocyclic group consisting of a fiveor six-membered ring containing nitrogen as ring member and, if desired, of condensed benzene rings, e.g., an oxazole, benzoxazole, naphthoxazole, thiazoline, thiazolc, benzothiazole, naphthothiazole, selenazole, benzoselenazole, naphthoselenazole, thiadiazole, imidazole, benzimidazole or 2- or 4-quinoline ring, which heterocyclic group may be further substituted; or b. a trimethine chain which carries in the mesoposition an alkyl group having up to five carbon atoms and in the terminal position an unsubstituted or substituted heterocyclic group as defined under (a); or a pentamethine or heptamethine chain which carries in the terminal position an unsubstituted or substituted heterocyclic group as defined under (a), and which chain may be substituted with alkyl having up to five carbon atoms, the three carbon atoms in 2-, 3- and 4- position or in 4-, 5- and 6-position of the said pentamethine or heptamethine chain together with a 2,2-

lOl007 0682 with epoxides such as ethylene oxide or l,2-propylene oxide or with derivatives of these compounds, e.g., with 3-phenoxy- 1,2-propy1ene oxide.

In these formulae the symbols R" and R'" have the meanings given above.

Depending on the conditions employed, one or more epoxide radicals can be added to the hydroxyl groups with opening of the ring to form (po1y)hydroxyalky1enated benzazoles or quinolines.

' For example when 1,2-propylene oxide is reacted with 2- methyl-S hydroxybenzothiazo1e using a molar ratio of 3:1, compound 1 is preferentially formed. However, when a molar ratio of 8 mols of 1,2-propy1ene oxide to 1 mol of 2-methy1-5- hydroxybenzothiazole is used, a mixture from which compounds 2 and 3 can be separated by fractional vacuum distillation is obtained. Compounds 4 to 9 are produced under the same conditions using ethylene oxide. For example, 2-methy1- mercapto-o-hydroxybenzothiazole when reacted with 1,2- propylene oxide yields compound 17. Compounds 10 to 15 are produced from 2-methyl-6-hydroxybenzothiazole, and 2- methyl-S-hydroxybenzose1enazo1e may be used to form compound 16. 6-hydroxy-quinaldine reacts with 3 to 6 mols of 1,2- propylene oxide to form a mixture of compounds 22 to 25 which can be separated by vacuum distillation.

When the hydroxyl-containing compound is reacted with 1,2-propylene oxide, opening of the epoxide ring may take place to produce either a primary alcohol or a secondary alcohol according to the reaction conditions; see Houben-Weyl Methoden der organischen Chemie, Vol. 14/2, 440 (see formula 19). The new benzazoles can be further worked up in known manner to produce cyanine dyes. This applies, for example, to compounds of the general formula A or to the individual compounds 1 to 25. The reaction is performed in known manner by quaternization, for example with dimethyl sulfate, ethyl-p-toluene-sulfonate or sultones and subsequent reaction with compounds of, for example, the following formula R" is as given above, 7 R is a hydrogen atom, or a methyl or ethyl group.

This reaction is described in detail, for example, in Germ an Pat. No. 710,748 and 1,072,765.

The preparation of some of these compounds is described below.

COMPOUND 1 1.4 g. of KOH and 27 g. of 1,2-propylene oxide are added to 48 g. of 2-methy1-5-hydroxybenzothiazole dissolved in 90 cc. of dioxane. The mixture is heated in an autoclave at 100 to 1 10 C. for hours. The reaction product is poured into water and the oil which precipitates is taken up in a large quantity of ether. The ether is dried and the ethereal solution concentrated by evaporation. About 45 g. of crude oil is obtained, to which a little ether (about 30 cc.) is added. The required substance crystallizes out on standing in the refrigerator and is recrystallized from ethyl acetate. The pure substance melts at 8 8 C.

COMPOUNDS 1-3 66 g. of 2-methy1-5-hydroxybenzothiazo1e, 200 cc. of dioxane, 3,2 g. of K011 and 200 g. of 1,2-propy1ene oxide are heated in an autoclave at 100 C. for 6 hours. The reaction product is poured into water and the oil which precipitates is extracted with chloroform. After the evaporation of the chloroform the residue is washed with water, taken up again in ether, dried and concentrated by evaporation. The residue amounts to 87 g. It is divided into four fractions by vacuum distillation;

0.2 mm.: 1. l30-170C., solidifies in the receiver 4. 220-260 C., very little, rejected.

The first fraction has a melting point of 88 C. after recrystallization. It is compound 1. Compound 2 is found in the second fraction. The third fraction consists of compound 3.

COMPOUNDS D4-9 90 g. of ethylene oxide is forced under pressure into 66 g. of 2-methyl-S-hydroxybenzothiazole dissolved in 450 cc. of diethylene glycol dimethyl ether in the presence of 2 g. of KOH in an autoclave. The reaction temperature is kept at 120 C. By pouring the reaction product into water and extracting with ether, an oil which can be separated into five fractions in vacuo is obtained.

The following fractions are obtained using a vacuum of 0.3

First fraction: 2002 1 8 C.: 22 g. ofcompound 5 Second fraction: 218-230 C.: 21 g. of compound 6 Third fraction: 246250 C.: 18 g. of compound 7 Fourth fraction: 261-275 C.: 18 g. ofcompound 8 Fifth fraction: 280-310 C.: 9 g. of compound 9 1f smaller quantities of ethylene oxide are used and a slightly lower temperature C.) is employed, the boiling point is found to be l75183 C. at 0.3 mm. and compound 4 is obtained.

COMPOUND U10 35 g. of 2-methy1-6-hydroxybenzothiazole, 15 g. of 1,2- propylene oxide, 160 cc. of dioxane and 1.5 g. of KOH are heated in an autoclave at 100 to C. for 6 hours. The reaction solution is poured into a large quantity of water. An oil separates out which solidifies in ice. After suction filtration and recrystallization from alcohol this is found to have an m.p. of 7678 C.

COMPOUNDS 12-15 47 g. of 2-methyl-6-hydroxybenzothiazo1e, 100 cc. of dioxane, 2 g. of KOH and g. of 1,2-propy1ene oxide are heated in an autoclave at 100 to 110 C. for 6 hours. The reaction mixture is worked up as described in example 1. The crude oil is fractionated in vacuo (0.4 mm.

First fraction: 218230 C., compound 12 Second fraction: 230-250C., compound 13 Third fraction: 250-260 C., compound 14 Fourth fraction: 270-290 C., compound 15.

COMPOUND 16 30 g. of 2-methyl-5-hydroxybenzoselenazole, 100 cc. of dioxane, 18 g. of 1,2-propy1ene oxide and 0.9 g. of KOH are heated in an autoclave for 5 hours at 90100 C. A substance which melts at 105 C. and the analysis of which corresponds to the given formula is obtained from the reaction product.

COMPOUNDS U22-25 COMPOUND 28 5.1 g. of compound 6 and 2.1 g. of dimethylsulfate are heated for a short time on a steam bath and the resulting quaternary salt is immediately further reacted without purification. lt is dissolved, together with g. of the compound in a mixture of 20 cc. of alcohol and 11 g. of phenol and heated to about 50 C., and 5.5 cc. of triethyl amine are added. After 24 hours, about 100 cc. of isopropanol are added to the concentrated dye solution, and crystallization of the dye starts after a short time. It is then removed by suction filtration and recrystallized from ethanol. M.p. 267l 68 C.

COMPOUND 35 7.5 g. of compound 17 are quaternized with 3.8 g. of dimethylsulfate, and the resulting salt is dissolved in 100 cc. of isopropanol together with 4.0 g. of N-ethylrhodanine. The dye starts to crystallize slowly after the addition of 5 cc. of triethylamine. It is recrystallized from a mixture of methanol and chloroform. M.p. 224C.

The same dye is obtained as follows: 17 g. of the dye of the following formula s llO@ s I 0 on, f

C2115 M.p. 325

24 g. of l,2-propylene oxide, 175 g. of N-methylpyrrolidone and 1.4 g. of solid KOl-l are heated in an autoclave at about 1 C. for 5 hours. The reaction mixture is poured into a dilute aqueous solution of NaCl and the precipitated dye is removed by suction filtration. The crude product is extracted several times with 250 ml. portions of ethyl alcohol. The first two extracts are rejected. Dye 35 crystallizes from the third and the following extracts. After recrystallization in the above-mentioned solvent mixture, an identical compound with a melting point of 224 C. is obtained.

The compounds according to the general formula A are valuable intennediates for the production of other heterocyclic compounds available in the different fields of chemistry such as pharmaceutical or photographic chemistry. Especially the compounds of the general formula B are very important for photographic aims as optical sensitizers for silver halide emulsions.

Some of the compounds of the general formula B, especially those trimethine dyes, in which R has the meaning (b) are excellent sensitizers to green light as will be shown in the examples.

Among the inventive compounds of the general formula B there is another group of sensitizing dyes in .which R' represents a pentamethine or heptamethine chain carrying in the end position a heterocyclic group. Correspondingly to the length of the polymethine chain the absorption and sensitization maxima are in the red or infrared region of the spectrum. The polymethine chain of said dyes may be substituted by alkyl groups and preferably in such manner that two methine groups in 2- and 4-position or in 4- and 6-position of the pentamethine or heptamethine chain are bridged by an alkyl substituted hydrocarbon chain, preferably by the neopentylene bridge, thus forming a 4,4-dimethyl-cyclohexene ring. Compound of this last-mentioned type comprising those shown by the formulae 45-49 are excellent sensitizers to red or infrared light. These compounds, in the preparation of which is used isophrone may also be called isophorone dyes."

The preparation of photographic silver halide emulsions substantially comprises three stages:

1. precipitations of the silver halide in the presence of a protective colloid and physical ripening,

2. removal from the emulsion of excess water-soluble salts which are produced on precipitation, generally by washing, and

3. chemical ripening or afterripening which serves to impart the desired sensitivity to the emulsion.

The sensitizing dyes according to the invention can be used in any silver halide emulsions.

Suitable silver halides are silver chloride, silver bromide or mixtures thereof, if desired with a small content of silver iodide of up to 10 mols percent. The silver halides may be dispersed in the usual hydrophilic compounds, for example in carboxymethylcellulose, polyvinyl alcohol, ployvinylpyrrolidone, alginic acid and its salts, esters or amides or preferably in gelatine.

The sensitizing dyes for use according to the invention are preferably added to the photographic emulsion after the chemical ripening and before casting. The methods used for this are generally known in the art. The sensitizing dyes are usually incorporated into the emulsion in the form of solutions. The solvents must, of course, be compatible with gelatine and must not have any adverse effect on the photographic properties of the emulsion. The quantity of sensitizing dye may vary within wide limits, e.g. between 2 and 200 mg., preferably between 10 and 60 mg. per kg. of silver halide emulsion. The concentration of dye can be varied to meet the particular requirements, depending on the nature of the emulsion and the desired sensitizing effect etc. The most suitable concentration for any given emulsion can be easily determined by the usual tests employed in photography.

The emulsions may also contain chemical sensitizers, e.g., reducing agents such as stannous salts, polyamines such as diethylene triamine or sulfur compounds such as those described in U.S. Pat. No. 1,574,944. The emulsions ma also contain salts of noble metals such as salts of ruthenium, rhodium, palladium, iridium, platinum or gold for chemical sensitization, as is described in the article by R. Koslowsky, Z. Wiss. Phot., 46 65-72 l The emulsions may also contain polyalkylene oxides, especially polyethylene oxide and derivatives thereof, as chemical sensitizers.

The emulsions penta-azaindenes, to the invention may contain the usual stabilizers, e.g. homopolar or salt-type compounds of mercury with aromatic or heterocyclic rings such as mercapto triazoles, simple mercury salts, sulfonium mercury double salts and other mercury compounds. Azaindenes, especially tetra or penta-azaindenes, in particular those which are substituted with hydroxyl or amino groups, are suitable as stabilizers. Such compounds are described in the article by Birr in Z.Wiss.Phot., 47, 2-58 (1952). Other suitable stabilizers are, inter alia heterocyclic mercapto compounds such as phenyl mercaptotetrazole, quaternary benzothiazole derivatives, benzotriazole and the like. The emulsions may be hardened in the usual manner, for example with formaldehyde or halogen-substituted aldehydes which contain a carboxyl group, such as mucobromid acid, diketones, methanesulfonic acids esters, dialdehydes and the like.

The spectral properties of some of the compounds according to the invention and those of two sensitizers of the following formulae used for comparison are summarized in the table below.

It will be seen from the above table that the sensitizcrs used for comparison and the compounds according to the invention absorb in the same region of the spectrum in alcoholic solution. The extinction is also substantially the same. The influence of monoether or polyether substituents only becomes noticeable in the sensitization of photographic emulsion where it is found that the sensitization maximum in the red region of the spectrum is shifted hypsochromically by substitution with an increasing number of either units and at the same time the green sensitivity is considerably increased. This effect is shown in the sensitization curves of the dyes and the sensitometric measurements of the sensitivities obtained using red and green wedges, as will be clear from the following examples.

Example 1 A highly sensitive silver bromide gelatine emulsion containing 3 mols percent of silver iodide and the usual additives, such as 0.35 g. of saponin as wetting agent, 3 ml. of an aqueous methanolic solution of N,N', N"-triacrylo-hexahydrotriazine( 13,5) percent) as hardener and 300 mg. of l,3,7-triaza-4hydroxyl-6-methylindolizine as stabilizer is divided into several parts.

The quantities of sensitizing dyes shown in the following table are added (per kg.) to the individual parts. The emulsions are then cast on a layer support in the usual manner and dried.

The layers obtained in this way are exposed in a conventional sensitometer behind step wedges with a density rise of V5 to red and green light. They are then developed and fixed in the usual manner. The relative sensitivities are expressed as the number of measurable steps obtained by exposure to red and green light.

TABLE 2 Sensitivity Dye quantity Sensitization in step 5 Dye No. mgJkg. maximum red green I 50 655 p. 2| l8 ll 50 650 p. 21-22 I) 26 50 635 p. 22 10 27 50 630 1.555 p. 20 22 28 50 625 11.540 .1 I9 23 29 50 625 .4550 u 18 22 The spectral sensitization curves of comparison dye l and of compounds 26 and 27 according to the invention are shown in the accompanying FIGS. 1A, 1B and 1C respectively. The considerable increase in the sensitivity in the green region of the spectrum is clearly visible.

Example 2 A silver bromide gelatine emulsion containing 2 mols percent of silver iodide and the other additives given in example I is sensitized as described there. The basic emulsion has a lower sensitivity than the emulsion used in example 1.

in this case the main effect observed is a relatively large increase in the green sensitivity. This is shown in the following table 3.

The spectral sensitization curves of the comparison compound l and of compound 28 and 29 according to the invention are shown in FIGS 2A, 2B and 2C respectively. The large increase in the range of the sensitizing effect in the green region of the spectrum is clearly visible.

Example 3 A highly sensitive silver halide gelatine emulsion containing 3.5 mols percent of silver iodide and the usual additives as described in example 1, is divided into several parts.

One part of the emulsion is sensitized with a comparison sensitizer of the following formula Se 0,115 -c H;

and the other part with compound 34 provided by the invention. The emulsion is then worded up as described in example 1.

The results of the sensitometric tests are given in the following table 4.

A silver bromide gelatine emulsion as used in example 3 is divided into several parts. One part of the above emulsion is sensitized with the comparison sensitizer l and the other with compound 37 of the invention.

The emulsions are then worked up as is described in example l. The results of the sensitometric tests are summarized in the following table 5.

TABLE 5 Sensitivity in mgJkg. maximum steps 1/? red green I S0 660 [L 20 I6 37 so 630 a l7 l8 We claim: 1. Spectrally sensitized photographic silver halide emulsion, containing a sensitizer of the following formula in which X is a sulphur, selenium or oxygen atom,.or a groupCll n is 1-5;

R is an ethyleneoxy or a 1,2-propyleneoxy unit;

R" is a saturated or unsaturated aliphatic group having up to five carbon atoms, which may be substituted with sulfonic acid, sulfamyl, carboxyl, carbamyl or hydroxyl groups or with -position halogen atoms;

R' is a monomethine group substituted with a fiveor sixmembered heterocyclic ring containing nitrogen as ring member; or a trimethine, pentamethine or heptamethine chain carrying in the terminal position an oxazole. benzoxazole, naphthoxazole, triazoline, thiazole. benzothiazole, napththothiazole, selenazole, benzoselenzole, napthoselenazole, thiadiazole, imidazole, benzimidazole or 2- or 4-quinoline ring, or a dimethine or tetramethine which carries in the terminal position a rhodanine, thiohydantoin, thiobarbituric acid or pyrazolone radical, or a rhodanine, thiohydantoin, thiobarbituric acid or pyrazolone radical.

2. Emulsion according to claim 1, wherein R is a trimethine chain which carries in the mesoposition an alkyl group having up to five carbon atoms.

3. Emulsion according to claim 1, wherein R is a pentamethine chain in which the three carbon atoms in 2-, 3- and 4-position of the said pentamethine chain together with a 2,2- dimethyl-trimethylene bridge form a 4,4-dimethyl-cyclohexene ring.

4. Emulsion according to claim 1, wherein X is sulfur or selenium. 

2. Emulsion according to claim 1, wherein RIII is a trimethine chain which carries in the mesoposition an alkyl group having up to five carbon atoms.
 3. Emulsion according to claim 1, wherein RIII is a pentamethine chain in which the three carbon atoms in 2-, 3- and 4-position of the said pentamethine chain together with a 2,2-dimethyl-trimethylene bridge form a 4,4-dimethyl-cyclohexene ring.
 4. Emulsion according to claim 1, wherein X is sulfur or selenium. 